The James Webb Space Telescope

The James Webb Space Telescope (JWST) is a large (6.6 m), cold (<50 K), infrared (IR)-optimized space observatory that will be launched early in the next decade into orbit around the second Earth–Sun Lagrange point. The observatory will have four instruments: a near-IR camera, a near-IR multiobject spectrograph, and a tunable filter imager will cover the wavelength range, 0.6 < ; < 5.0 μ m, while the mid-IR instrument will do both imaging and spectroscopy from 5.0 < ; < 29 μ m.The JWST science goals are divided into four themes. The key objective of The End of the Dark Ages: First Light and Reionization theme is to identify the first luminous sources to form and to determine the ionization history of the early universe. The key objective of The Assembly of Galaxies theme is to determine how galaxies and the dark matter, gas, stars, metals, morphological structures, and active nuclei within them evolved from the epoch of reionization to the present day. The key objective of The Birth of Stars and Protoplanetary Systems theme is to unravel the birth and early evolution of stars, from infall on to dust-enshrouded protostars to the genesis of planetary systems. The key objective of the Planetary Systems and the Origins of Life theme is to determine the physical and chemical properties of planetary systems including our own, and investigate the potential for the origins of life in those systems. Within these themes and objectives, we have derived representative astronomical observations.To enable these observations, JWST consists of a telescope, an instrument package, a spacecraft, and a sunshield. The telescope consists of 18 beryllium segments, some of which are deployed. The segments will be brought into optical alignment on-orbit through a process of periodic wavefront sensing and control. The instrument package contains the four science instruments and a fine guidance sensor. The spacecraft provides pointing, orbit maintenance, and communications. The sunshield provides passive thermal control. The JWST operations plan is based on that used for previous space observatories, and the majority of JWST observing time will be allocated to the international astronomical community through annual peer-reviewed proposal opportunities.     

Flare build-up study — Homologous flares group — Part I

According to the definition of the homology (optical) kept in reference, the homologous flares (HFl) may be observed wherever flares occur. The supposed supplementary preflaring conditions to have HFl may be either that the preflaring conditions have not been destroyed by the first flare (and then what mechanism has stopped the first and triggered the second ?) or that the preflaring conditions have been destroyed and rebuilt (and then, how ?). The analysis of data related to some selected active regions AR by the members of the working group, and the earlier works on HFl, may be used simultaneously to investigate the differences between one set of HFl and the others, the location of their sites and the evolution of HFl productive AR. This study brings the appearance of new footpoints from one flare to the following, the behaviour of cool arches (surging arches) leading to information on the changes of the magnetic configuration, and to peculiar characteristics of HFl, oif 2nd, 3rd in the time order concerning the chromospheric transition zone or coronal regions. The time delay between two consecutive homologous flares appears very quickly as an essential parameter to study homology. It was found that every set of flares (same type of site) is able to produce “rafales” of homologous flares, i.e. two, three, four, oir more flares with Δt in the range of one hour or less. The observations show no great chantes in macroscopic photospheric patterns (B, V) during this H flaring period. They lead to compare their temporal variation curves of flare brightness. A quantitative brightness parameter of homology relation has been defined. Some scale changes have also been detected in the dynamic spectrum of the site, and it is in good agreement with a very interesting theoretical suggestion made by P. Sturrock to produce such “rafales”. It may be shown that the closely consecutive time-homologous flares (CCHF) or “rafales” represent a good tool to analyse the critical conditions related to the origin and the amount of energy, mechanism of storage and release, necessary and, perhaps, sufficient conditions. New statistical results, applied to the different selected homologous flare active regions are presented and show the existence in homologous flaring areas of a “pivot” of previous filaments interpreted as a signature of an anomaly in the Solar rotation.     

A small mission for in situ exploration of a primitive binary near-Earth asteroid

We present a concept for a challenging in situ science mission to a primitive, binary near-Earth asteroid. A sub-400-kg spacecraft would use solar electric propulsion to rendezvous with the C-class binary asteroid (175706) 1996 FG3. A campaign of remote observations of both worlds would be followed by landing on the ∼1 km diameter primary to perform in situ measurements. The total available payload mass would be around 34 kg, allowing a wide range of measurement objectives to be addressed. This mission arose during 2004 from the activities of the ad-hoc Small Bodies Group of the DLR-led Planetary Lander Initiative. Although the particular mission scenario proposed here was not studied further per se, the experience was carried over to subsequent European asteroid mission studies, including first LEONARD and now the Marco Polo near-Earth asteroid sample return proposal for ESA’s Cosmic Vision programme. This paper may thus be of interest as much for insight into the life cycle of mission proposals as for the concept itself.     

Algebraic turbulent energy flux models for hypersonic shear flows

Algebraic truncation models were derived for the turbulent energy flux for high-speed shear flows with and without thermal and mechanical non-equilibrium effects. To facilitate closure, fluctuating dilatation moments were modeled via conservation of mass truncations and the inhomogeneous terms were neglected. The resulting energy flux model provided significant improvements, up to 20%, in the temperature predictions over the gradient diffusion model for equilibrium flows over a Mach number range of 0.02–11.8. Our experiments showed that vibrational relaxation significantly altered the basic decay rate of grid turbulence. Also, our models indicated that compressibility introduces an explicit pressure gradient dependency. Analyses of a governing parameter indicated that these terms are negligibly small for low speeds, but may be important, or even dominant, for high-speed flows.     

Information theory,animal communication,and the search for extraterrestrial intelligence

We present ongoing research in the application of information theory to animal communication systems with the goal of developing additional detectors and estimators for possible extraterrestrial intelligent signals. Regardless of the species, for intelligence (i.e., complex knowledge) to be transmitted certain rules of information theory must still be obeyed. We demonstrate some preliminary results of applying information theory to socially complex marine mammal species (bottlenose dolphins and humpback whales) as well as arboreal squirrel monkeys, because they almost exclusively rely on vocal signals for their communications, producing signals which can be readily characterized by signal analysis. Metrics such as Zipf's Law and higher-order information-entropic structure are emerging as indicators of the communicative complexity characteristic of an “intelligent message” content within these animals’ signals, perhaps not surprising given these species’ social complexity. In addition to human languages, for comparison we also apply these metrics to pulsar signals—perhaps (arguably) the most “organized” of stellar systems—as an example of astrophysical systems that would have to be distinguished from an extraterrestrial intelligence message by such information theoretic filters. We also look at a message transmitted from Earth (Arecibo Observatory) that contains a lot of meaning but little information in the mathematical sense we define it here. We conclude that the study of non-human communication systems on our own planet can make a valuable contribution to the detection of extraterrestrial intelligence by providing quantitative general measures of communicative complexity. Studying the complex communication systems of other intelligent species on our own planet may also be one of the best ways to deprovincialize our thinking about extraterrestrial communication systems in general.     

The Israeli satellite launch: Capabilities, intentions and implications

The launch of the Israeli satellite Ofeq-1 during September 1988 has significant regional and global implications. These include the proliferation of both surveillance satellites and ballistic missiles, the latter having the potential to deliver conventional, chemical and nuclear warheads to areas situated many hundreds of miles away. This paper addresses both the origins of the Israeli booster technology and the many implications of the satellite launch. It then speculates on their political and arms control consequences. It concludes that in light of the parallelism that has evolved between nuclear and chemical weapons and ballistic missiles, there is an increasing need to develop global and, if appropriate, regional and bilateral strategies to limit missile proliferation and bring the issue to the forefront of international political debate.     

The pharao project: Towards a space clock using cold cs atoms

For several years, the “BNM-Laboratoire Primaire du Temps et des Fréquences” has worked on a cold atom frequency standard. With a cesium atomic fountain a resonance line width of 700 mHz has been obtained leading to a short-term stability of 2 × 10⁻¹³ τ^−1/2 down to 2 × 10⁻¹⁵ at 10⁴ s. A first evaluation of the fountain accuracy has been performed resulting in an accuracy of 3 × 10⁻¹⁵, three times better than previously achieved with thermal beams frequency standards. In the atomic fountain, gravity limits the interaction time to ˜1 s, hence the resonance line width to ˜0.5 Hz. A factor of 10 reduction in the line width could be obtained in a micro-gravity environment. The “Centre National d'Etudes Spatiales” (the French space agency), the “BNM-Laboratoire Primaire du Temps et des Fréquences”, the “Laboratoire de l'Horloge Atomique” and the “Laboratoire Kastler Brossel” have set up a collaboration to investigate a space frequency standard using cold atoms: the PHARAO project. A microgravity prototype has been constructed and operated first in the reduced gravity of aircraft parabolic flights in May 1997. It is designed as a transportable frequency standard. The PHARAO frequency standard could be a key element in future space missions in fundamental physics such as SORT (solar orbit relativity test), detection of gravitational waves, or for the realization of a global time scale and a new generation of positioning system.     

EXPOSE-E: an ESA astrobiology mission 1.5 years in space

The multi-user facility EXPOSE-E was designed by the European Space Agency to enable astrobiology research in space (low-Earth orbit). On 7 February 2008, EXPOSE-E was carried to the International Space Station (ISS) on the European Technology Exposure Facility (EuTEF) platform in the cargo bay of Space Shuttle STS-122 Atlantis. The facility was installed at the starboard cone of the Columbus module by extravehicular activity, where it remained in space for 1.5 years. EXPOSE-E was returned to Earth with STS-128 Discovery on 12 September 2009 for subsequent sample analysis. EXPOSE-E provided accommodation in three exposure trays for a variety of astrobiological test samples that were exposed to selected space conditions: either to space vacuum, solar electromagnetic radiation at >110?nm and cosmic radiation (trays 1 and 3) or to simulated martian surface conditions (tray 2). Data on UV radiation, cosmic radiation, and temperature were measured every 10?s and downlinked by telemetry. A parallel mission ground reference (MGR) experiment was performed on ground with a parallel set of hardware and samples under simulated space conditions. EXPOSE-E performed a successful 1.5-year mission in space.     

From Initial Models of Seismicity,Structure and Noise to Synthetic Seismograms for Mars

The InSight mission will land a single seismic station on Mars in November 2018, and the resultant seismicity catalog will be a key component for studies aiming to understand the interior structure of the planet. Here, we present a preliminary version of the web services that will be used to distribute the event and station metadata in practice, employing synthetic seismograms generated for Mars using a catalog of expected seismicity. Our seismicity catalog consists of 120 events with double-couple source mechanisms only. We also provide Green’s functions databases for a total of 16 structural models, which are constructed to reflect one-dimensional thin (30 km) and thick (80 km) Martian crust with varying seismic wave speeds and densities, combined with two different profiles for temperature and composition for the mantle. Both the Green’s functions databases and the precomputed seismograms are accessible online. These new utilities allow the researchers to either download the precomputed synthetic waveforms directly, or produce customized data sets using any desired source mechanism and event distribution via our servers.

     

Effects of restitution,friction, and attitude on 2D low-velocity rigid-body impacts

The impact of nonspherical bodies is complex, even at low velocities where contacting bodies are assumed to be rigid. Models of varying complexity (e.g. finite element methods) can be used to evaluate such impacts, but it is advantageous to use impulsive models such as that by Stronge, which are computationally inexpensive and governed by (fixed) material interaction coefficients. Stronge’s model parameterizes nonspherical rigid-body impacts with energetic restitution and Coulomb friction coefficients. This model was successfully used in large-scale simulations of ballistic lander deployment to asteroids and comets, whose trajectories involve dozens of chaotic bounces. To better understand the complex dynamics of these bouncing trajectories, this paper performs a dedicated study of idealized bouncing in two dimensions and on a flat plane, in order to limit the involved degrees of freedom. Using a numerical implementation of Stronge’s model, the motion of a bouncing square is simulated with different impact conditions: the square’s impact attitude, velocity, and mass distribution as well as the surface restitution and friction coefficients. The simulation results are used to investigate how these conditions affect the bouncing motion of the square, with a distinction between first impacts with zero angular velocity and successive impacts in which the square is spinning. This reveals how a single “macroscopic” bounce that separates two ballistic arcs may often consist of multiple micro-impacts that occur in quick succession. For the different impact conditions, we show how the number of micro-impacts per macro-bounce varies, as well as the normal, tangential, and total kinematic restitution coefficients. These are different from the energetic material restitution coefficient that parameterizes the impact. Finally, we examine how the settling time and distance of the bouncing trajectories change. These trends provide insight into the bouncing motion of ballistic lander spacecraft in small-body microgravity.